We consider a horizontal liquid-filled square capillary of width and height \(D\)  in a Cartesian three-dimensional domain, \(\textbf {x} = (x,y,z)\) , with an elongated gas bubble propagating through its interior (see figure REF ). Assuming incompressible flow, Newtonian fluids, and negligible gravitational effects, we perform direct numerical simulations (DNS) based on the two-phase Navier-Stokes equations and a hybrid front-tracking/level-set method to handle the interface and surface tension forces. This method, as formulated and implemented in [1]}, is coupled with the resolution of surfactant transport and exchange between the interface and the liquid phase bulk, as described in [2]}. The relevant variables involved in the system have been rendered dimensionless (denoted by tildes) by using the scalings depicted in Eq. (REF ),
\(\begin{split}\tilde{\textbf {x}}=\frac{\textbf {x}}{D},~\tilde{\textbf {u}}=\frac{\textbf {u}}{U_{a}} ,~\tilde{t}=\frac{t}{D/U_{a}},~\tilde{p}=\frac{p}{\rho _{l}U^{2}_{a}},~\tilde{\sigma } = \frac{\sigma }{\sigma _s},~\\\tilde{\Gamma }=\frac{\Gamma }{\Gamma _\infty },~\tilde{C}=\frac{C}{C_{\infty }},~\tilde{C_s}=\frac{C_s}{C_{\infty }},\end{split}\) 
